The invention is directed to a device for spreading radar chaff from airplanes, comprising a magazine for holding chaff bundles which can be displaced towards an ejection opening by means of a controllable displacement member. The chaff is ejected into the surrounding air stream and spread by air turbulence.
In the following description the word chaff will be used as a designation of the radar interference means used and should be considered to include the usual metal foil strips as well as corresponding means, e.g. metal covered glass fibers.
Devices of the type mentioned above are known and are used for forming chaff clouds. A chaff cloud of this type may consist of a very large number of strips supplied by the bundles and forming dipoles of predetermined lengths. Dependent on the lengths of the dipoles, frequency bands which are used for radar reconnaissance, homing missiles and corresponding objects will be interfered with.
Prior art devices for spreading radar chaff usually have one of three different forms of construction. In the first form the spreading device is capsule shaped and attached to one of the beams or other weapon support means on the airplane. In the second form the spreading device is attached to the outer shell of the airplane body. In the third form the spreading device is contained within the airplane body.
These three forms of construction have different advantages and drawbacks. The two last mentioned forms require modification of the airplane body. If the spreading device is mounted on the shell of the airplane, the weight and dimensions thereof, and thereby its chaff capacity, will have to be limited in order to avoid extensive constructional reinforcements of the associated parts of the airplane body. The device might also disturb aerodynamic flow around the airplane body, adversely affecting chaff spreading. The last mentioned drawback also applies to the third form which has the further drawback that special space must be allocated within the airplane body. Normally no such space is available in an existing airplane, but will have to be planned during development of the airplane.
The capsule-shaped device which attaches to weapon support means effectively spreads chaff, has a large chaff capacity, and can be attached to existing support means. The drawbacks of such a device are that it will occupy a position on the airplane which could otherwise be used for attaching weapons and it has a relatively high air resistance and weight. A spreading device of this type is known from Swedish patent application No. 7606167-0 corresponding to U.S. Pat. No. 4,134,115.